apt-get install build-essential    # build-essential packages, include binary utilities, gcc, make, and so on
apt-get install man                # on-line reference manual
apt-get install gcc-doc            # on-line reference manual for gcc
apt-get install gdb                # GNU debugger
apt-get install git                # revision control system
apt-get install libreadline-dev    # a library used later
apt-get install libsdl2-dev        # a library used later
apt-get install llvm llvm-dev      # llvm project, which contains libraries used later
apt-get install llvm-11 llvm-11-dev # only for ubuntu20.04